Its a different emphasis. I don't think it is an attack to point out something that is true. There is no point denying it. Here is how I look at it:
If you swapped President Hillary, Sanders, Biden, or even Elizabeth Warren and kept everything else constant about the current political situation, there really wouldn't be any difference in terms of big Democratic agenda items like gun control because the Republicans would control at least the House. Unfortunately, Republicans are pretty much locked into control of at least the House for the foreseeable future mainly because of geography. Gerrymandering plays a part, but even absent that, demographics that tend to vote Republican tend to dominate rural areas, while demographics that tend to vote Democratic tend to concentrate in urban and suburban areas.
As it relates to gun control, people in rural areas tend to view guns very differently than people in urban and suburban areas. I spent four years in central Pennsylvania. Out there, schools have off for the first day of hunting season, and even the top 40 station has adds on the radio for gift certificates to the local gun store. I visited a town where the biggest building was a large warehouse with the word "guns" printed in huge letters on the roof. The problem for Democrats is that these people vote; they don't really like gun control; and they hold disproportionate political power due both to gerrymandering and the geography of this country.
To me, all that means that its almost impossible for Democrats to pass aggressive gun control legislation in the current political environment. I think you would need disasters on the scale of the Iraq War, Katerina, Bush's attempt to partially privatize social security, and the financial crisis to get voters in rural areas in many states to switch back to the Democrats as they did between 2006 and 2010. And then, if Democrats did manage to pass gun control legislation, they would simply get voted out again like the did in 2010 and 1994. I spent too much time in 2012 and 2014 hoping that Obama's coattails or voter disgust with Republicans threatening to shut down the government would flip the House back to the Democrats. It just isn't happening. Sadly, the issue of gun control especially is a wedge issue that seems to irrevocably divide rural voters from urban and suburban voters.
Believe it or not, stuff like "taking on banks" actually enjoys more popular support among people in both urban and suburban areas than something like gun control. From what I can tell, the Sanders people are trying to build a coalition centered around economic issues that can win in both urban and rural areas. I'm not sure if that will work, but that is the theory. Such an emphasis would probably tend to deemphasize the pursuit of very aggressive gun control legislation, or at least cause Sanders to not want to appear to be the furthest left on that issue.
I understand all of that is upsetting in light of the clear need to do something about gun violence, but it is what it is. I just don't see aggressive, or realistically any gun control passing right now because I still think the Republicans are going to control at least the House regardless of who wins the Presidency.